Removing bevel on radio button in Adobe Acrobat Forms

If you convert a PDF document into an editable PDF form using Adobe Acrobat, it creates a small solid border around the radio buttons.

However sometimes you have to add your own, in by default they come with a bevelled edge.

How do you remove this? At first it looks like you can't. However you can.

Choose a border colour and a fill colour. At this point the Line Style becomes enabled and is set to "Inset". Change this to solid, and then set the border colour and fill colour back to "No colour". Bingo!